I'm thinking about buying my first handgun for home defense and to shoot at the range. It will be the M&P since I like how it felt in my hands and its so light compared to other guns I held. I just cannot decide if I should go with 9mm or .40 caliber. Other than 9mm ammo being little cheaper is there another reason I should not look at the .40? What do you guys think? Also how much recoil difference is between them?